Dose and time-course evaluation of a redox-based estradiol-chemical delivery system for the brain. I. Tissue distribution.
Brain-enhanced delivery and sustained release of estradiol (E2) may be potentially useful in the treatments of vasomotor hot flushes and prostatic adenocarcinoma and for fertility regulation. Therefore, we have evaluated a redox-based estradiol-chemical delivery system (E2-CDS) for the brain. The mechanism of this drug delivery is based on an interconvertible dihydropyridine in equilibrium pyridinium salt redox reaction. In this study, we investigated the dose- and time-dependent effects of E2-CDS on the tissue distribution of E2-Q+ and E2, the inactive (intermediate) and active metabolites, respectively, of the E2-CDS. Ovariectomized rats received a single iv injection of E2-CDS at 0.01, 0.1, or 1.0 mg/kg or an E2 dose of 0.7 mg/kg or the drug's vehicle, 2-hydroxypropyl-beta-cyclodextrin (HPCD), on day 0. Tissue samples including brain and peripheral tissues were then analyzed for both E2-Q+ and E2 at 1, 7, 14, 21, or 28 days following the E2-CDS administration. Initially, both E2-Q+ and E2 were detected in all tissues analyzed. The dose-distribution and time-course study demonstrates that (1) at 24 hr (1 day) after administration of E2-CDS, all tissues showed a dose-proportional increase in concentrations of E2-Q+ and E2; (2) the enzymatic oxidation of E2-CDS to E2-Q+ was dose dependent over the 100-fold dose range examined; and (3) the disappearance of E2-Q+ as well as E2 was slow in whole brain and hypothalamus, with an apparent t1/2 = 8-9 days, while both of these metabolites were rapidly cleared from plasma, liver, fat, anterior pituitary, kidney, lung, heart, and uterus.(ABSTRACT TRUNCATED AT 250 WORDS)
Rahimy
M H
MH
Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville 32610.
Simpkins
J W
JW
Bodor
N
N
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D004958:Estradiol / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D005260:Female; D006868:Hydrolysis; D010084:Oxidation-Reduction; D011863:Radioimmunoassay; D051381:Rats; D014018:Tissue Distribution / Q000502:physiology
D004337:Drug Carriers; D004958:Estradiol